Genome-wide screening for components of small interfering RNA (siRNA) and micro-RNA (miRNA) pathways in the brown planthopper, Nilaparvata lugens (Hemiptera: Delphacidae).

The brown planthopper (BPH), Nilaparvata lugens, is a major rice pest in Asia, and accumulated evidence indicates that this species is susceptible to RNA interference (RNAi); however, the mechanism underlying RNAi and parental RNAi has not yet been determined. We comprehensively investigated the repertoire of core genes involved in small interfering RNA (siRNA) and micro-RNA (miRNA) pathways in the BPH by comparing its newly assembled transcriptome and genome with those of Drosophila melanogaster, Tribolium castaneum and Caenorhabditis elegans. Our analysis showed that the BPH possesses one drosha and two Dicer (dcr) genes, three dsRNA-binding motif protein genes, two Argonaute (ago) genes, two Eri-1-like genes (eri-1), and a Sid-1-like gene (sid-1). Additionally, we report for first time that parental RNAi might occur in this species, and siRNA pathway and Sid-1 were required for high efficiency of systemic RNAi triggered by exogenous dsRNA. Furthermore, our results also demonstrated that the miRNA pathway was involved in BPH metamorphosis as depletion of the ago1 or dcr1 gene severely impaired ecdysis. The BPH might be a good model system to study the molecular mechanism of systemic RNAi in hemimetabolous insects, and RNAi has potential to be developed to control this pest in agricultural settings.

Identification and biochemical characterization of Laodelphax striatellus neutral ceramidase.

Ceramidases are a group of enzymes that catalyse hydrolysis of ceramides to generate fatty acid and sphingosine. In this study, we report the cloning and characterization of the rice small brown planthopper Laodelphax striatellus neutral ceramidase (nCDase), LsnCer. LsnCer was identified by sequencing the transcriptome of L. striatellus and is a protein of 717 amino acids with a predicted molecular weight of 79.3 kDa. Similarly to other known nCDases, the optimum pH for LsnCer is 8.0 and the optimum temperature is 37 °C for its in vitro activity. LsnCer activity is inhibited by Zn(2+) significantly and Fe(2+) slightly. LsnCer has broad substrate specificity with a preference for ceramides with a medium acyl-chain or a monounsaturated long acyl-chain. Infection with rice strip virus (RSV) or treatment with insecticides significantly increased LsnCer mRNA expression and its enzymatic activity in L. striatellus. These results suggest that LsnCer is a bona fide nCDase that may have a role in adaption of L. striatellus to environmental stresses.

Post-earthquake outbreak of insecticide-associated conjunctivitis in a primary school of Lixian district, China: An epidemiological investigation.

OBJECTIVES: To describe the time course and characteristics of an insecticide-associated incident and highlight potential risks from similar outbreaks that may occur in other areas to enhance the preparedness of emergency physicians and other healthcare providers to deal with the sequelae of these events. STUDY DESIGN: Outbreak investigation METHODS: From 5 to 8 August 2008, an outbreak investigation was carried out among the affected primary school located in the refugee camp area of Lixian district, Sichuan, China. Affected pupils, parents, teachers and doctors working in the local medical stations were visited. Clinical checking, clinical treatment, epidemiological investigation and environmental investigation were undertaken. RESULTS: In total, 138 individuals were diagnosed with acute conjunctivitis, characterized by inflammation of the conjunctiva and intense ocular symptoms such as redness, itching and mucus discharge. According to the results, all risk factors (i.e. drinking water, indoor air and the materials used in camp classrooms) were excluded except insecticide exposure. The characteristics of symptoms, distribution of cases and records of irregular insecticide spraying support the assumption that the conjunctivitis outbreak was associated with synthetic pyrethroid alphacypermethrin exposure. CONCLUSION: The results suggest that non-standard operating procedures in pest control could lead to disease incidents. Medical rescue teams should receive training and education in preventive techniques.

Effects of transgenic rice expressing Bacillus thuringiensis Cry1Ab protein on ground-dwelling collembolan community in postharvest seasons.

During 2005-2008, field studies were conducted at two locations in Chongqing, China, to assess the potential effects of transgenic rice expressing Bacillus thuringiensis (Bt) Cry1Ab protein on the nontarget ground-dwelling collembolan community in three postharvest seasons. Collembolans in non-Bt and Bt rice fields were sampled with pitfall traps during each of two postharvest seasons of 2005/2006 and 2006/2007 and litterbag traps during each of three postharvest seasons of 2005/2006, 2006/2007, and 2007/2008. Ground-dwelling collembolans in rice fields during the postharvest seasons were abundant, whereas community densities varied considerably between the two locations and among the three seasons. A total of 67,310 collembolans, representing three species, Entomobrya griseoolivata, Hypogastrura matura, and Bourletiella christianseni, were captured during the three postharvest seasons. E. griseoolivata was the predominant species, accounting for 87.7% of the total captures, followed by H. matura (10.7%) and B. christianseni (1.6%). In general, there were no significant differences in species compositions and abundances of each species between Bt and non-Bt paddy fields, suggesting no significantly impact of plant residues of Cry1Ab rice on collembolan communities during postharvest seasons.

Cloning, expression and functional analysis of a general odorant-binding protein 2 gene of the rice striped stem borer, Chilo suppressalis (Walker) (Lepidoptera: Pyralidae).

A full-length cDNA encoding a general odorant binding protein 2 (GOBP2) was cloned from the antennae of the rice striped stem borer, Chilo suppressalis (Lepidoptera: Pyralidae), by the combination of reverse transcription PCR (RT-PCR) and rapid amplification of cDNA ends PCR (RACE-PCR). The cDNA contains a 489 bp open reading frame, which encodes a 162 amino acid protein, termed as Ch. suppressalis GOBP2 (CsupGOBP2). CsupGOBP2 is similar in the number of amino acids and protein sequence to GOBP2s in other species of Lepidoptera. RT-PCR results showed that CsupGOBP2 mRNA was highly expressed in the adult antennae of both females and males, as was CsupGOBP2 protein as revealed by Western blot analysis. CsupGOBP2 expressed in Escherichia coli was purified by affinity chromatography, refolding and gel filtration from the inclusion body. Fluorescence emission spectra and competitive binding assays by using N-phenyl-1-naphthylamine as first binding ligand and odorants as potential competitors revealed that the CsupGOBP2 protein has significant affinity to cis-11-hexadecenal (Z11-16:Ald), the main component of Ch. suppressalis pheromone and to laurinaldehyd and benzaldehyde, two general plant volatile aldehydes.